1. Field of the Invention
The present invention concerns a packaging device, used to package or tie together steel plate wrapped coils, steel bundles and the like, by tying a packaging material around the surface of the item for packaging, so that the item for packaging can be easily handled and in order to prevent the item for packaging from getting dirty. Specifically, the invention concerns a packaging device which, on the one hand, can be used for packaging relatively large items for packaging, yet its structure is simple and can be miniaturized.
2. Description of the Prior Art
In the past, packaging devices of steel plate wrapped coils included, for example, the device disclosed in Japanese Patent Application 5-294314, which consisted of a circular track, forming a closed route, and constructed so that one part thereof can open and close, a truck, revolving on top of the above-mentioned circular route, a means of feeding a packaging material, which is mounted on the above-mentioned truck to feed the packaging material from a packaging material coil. A means of support, which can support the item for packaging and whose one part was closed was set in the above-mentioned circular route.
According to the above-mentioned existing technology, as shown, for example, in FIG. 3, a truck (51) is set so that it can pass inside the steel plate wrapped coil, which is the item for packaging, while a motor (52) and a current collector (53) are mounted on the truck (51). Conductive rails (55) are arranged along a circular track (54), to supply electric power, via the current collector (53), to motor (52), to run the truck (51).
In addition, because the distance between the item for packaging and the truck (51), surrounding its circumference, varies from one time to another, a tension accumulator (58) is installed on the truck (51), in order to prevent slackening of the packaging material (57) delivered from the packaging material coil (56), which is on the truck (51), when this distance narrows.
In other words, several stationary guide rollers (59) and several swinging guide rollers (60) are arranged, and if the swinging guide rollers (60) move away from the stationary guide rollers (59), the packaging material (57), which revolves the guide rollers (59,60) and moves along a curved route, is slackened and thus the swinging guide rollers (60) applies a constant tension to the packaging material (57), as it moves away.
The above-mentioned existing packaging device has the following problems.
(1) Because the motor is installed in the truck, the truck must to be large, and in order to enable this truck to revolve smoothly, the radius of curvature in the corners has to be large, likewise, the circular track has to be large, and the whole packaging device becomes enlarged. In addition, because the conductive rails are laid along the circular track, electrical leak counter-measures have to be sufficiently installed to maintain operator safety, and the whole packaging device is therefore enlarged also for this reason. PA0 (2) In the tension accumulator, which consists of several stationary guide rollers and several swinging guide rollers, in addition to an urging means, in order for the swinging guide rollers to move smoothly, space has to be created on the truck, and the truck has to be enlarged even more. As a result, the circular track has to be enlarged and the whole packaging device is further enlarged.
In addition, although it may seem that by increasing the number of guide rollers, the movement distance of the above-mentioned swinging guide rollers can be decreased, in such a case, the resistance produced between the guide rollers and the packaging material increases, the smooth movement of the swinging guide rollers is interrupted, and especially in devices wherein the truck revolves at a high speed, they cannot respond quickly to rapid changes in the tension of the packaging material.